Last week, we had the author of TDD for a Shopping Website LiveProject. Friday at 11am Ranch time, Steven Solomon will be hosting a live TDD session just for us. See for the agenda and registration link
First of all, you should take a look at this tutorial about Strings and StringBuffers. This should give you a good introduction to the tools available to solve this task. You should also familiarize yourself with the Java API docs. This will give you a handy reference to the classes and methods available from the standard Java API. It is certainly worth your time to learn how to navigate this. For now, you should start by finding the classes in the java.lang package since that is where String and StringBuffer are located.